Reference may be had to the April 1970 Bell System Technical Journal articles on Page 587 entitled "Charge Coupled Semiconductor Devices" by W. S. Boyle and G. E. Smith for a background description of the device. Essentially at the risk of starting again what others have said over and over, a charge coupled device consists of a metal insulator semiconductor structure in which minority carriers are stored in a well, which can be termed a boat filled with electrons at the surface of the semiconductor, so that the charge may be moved along the surface by moving the potential minimum.
Other prior art references in the area of concern of this invention were noted in chronological order of disclosure to be:
A. charge coupled device shift register read/write/regeneration circuit, l. m. terman, IBM Technical Disclosure Bulletin, 14 No. 12:3784-3785, May 1972; PA1 B. u.s. pat. Nos. 3,806,772-3, 852,801 and 3,867,645; and PA1 C. published patent application B 309,755 of Jan. 28, 1975, now U.S. Pat. No. 3,919,468.
In this prior art a typical low noise input structure has a capacitance of the well located under the input electrode to be typically 1.0 Picofarad as are the capacitances under the successive adjacent array elements. These devices can only store a small charge at the operating voltages of conventional integrated circuits (IC's.) This small charge exhibits quantum variations (noise) of such a magnitude that only voltages greater than tens of millivolts can be applied to the input if the output signal-to-noise ratio greater than one is desired, even for audio band widths.
It has been found that attempts to alleviate the above by scaling up the size of the input electrodes, and thereby the electrode capacitances to allow acceptances of microvolt signals requires too much physical space on the substrate surface to be practical: The factor is at least 10 to 1. Furthermore, the voltage fields associated with such large capacitors would not collapse properly when the switching voltages were changed in order to shift the signal.
This invention differs from the prior art significantly in providing a structure whereby data entry is via increasing area and capacitance of an input electrode to increase the potential accumulating of a charge. This is structurally possible by this invention's disclosure to the art of switch means electrically connecting together several adjacent clocking electrodes during data entry and then with the teachings of this invention using a portion of the switch means to cause the clocking electrodes to regain their identity during a data load phase whereby they sequentially sweep successive portions of the accumulated charge towards a gate which is then operated to sweep the charge into, for example, a shift register.
Another object of this invention is to, therefore, disclose how one can in such a device achieve a capacitance about one-tenth that under the previously clocked input electrode whereby a proportional voltage gain results to give a signal-to-noise advantage as the data is shifted through the device.
A more detailed object with which reference was made above is to provide a very low noise input capability for a charge coupled device and simultaneously provide a voltage gain in each electrode of the device prior to or in conjunction with the transfer of the signal(s) into the shift register to provide a signal gain that insures the amplitude of the signal will be well above the noise level associated with the shift register of the charge coupled device.
A more specific object of this invention is the use of switches to increase the area of the well associated with an input electrode and thereafter subdivide the input into discrete electrodes consisting of one or more sets of clocking electrodes that will sweep the charge along from under one electrode to the next whereby a well capacitance of 10.0 Picofarads will in proportion to that under the electrodes of 1.0 Picofarad provide a voltage increase of 10 without serious degradation by extraneous noise associated with a multiplexing process such as described.
Other objects and advantages will appear from the drawings and their description that follows.